Magnetic material



atented ay 15, 1928.

CHARLES PHILIP BEATH, OI CHICAGO, AND HERBERT MARTIN EDABD HEINICKE,

F ELGIN, ILLINOIS, ASSIGNORS TO- WESTERN ELECTRIC COMP INCOBPO= TED, NEWYORK, N. 1., A CORPORATION 03 NEW YORK.

MAGNETIC MATERIAL.

Ho Drawing.

This invention relates to methods of producing magnetic materials, andmore particularly to methods of produc ng brittle magnetic alloys foruse in electrical signal- 5 ing apparatus, such as cores for loadingcoils employed in telephone circults.

The principal object of the invention 1s the production of a brittlemagnetic material, having a'fine crystalline structure, to

facilitate its reduction to a very finely d1- vided form, and possessingto a high degree those physical, electrical and magnetic propertieswhich make it highly desirable in electrical signaling apparatus,especially m 35 cores for loading coils for telephone circuits.

The magnetic material produced 1n accordance with the invention is ofparticular advantage in the production of magnet cores of the so-calleddust type in which a magac netic material is reduced to very finelydivided particles, the particles covered with a suitable insulatingmaterial and pressed lnto rings or cores. It is especially adapted to beused in connection with the insulating as material and in the mannermore full described in the copending application, erial No. 102,729,filed April 17, 1926, by J. W. Andrews and R. Gillis. However, themagnetic material is not limited in its use to the particular insulatordisclosed in the foregoing application nor to any particular form ofcore, but may be put to any use within the scope of the appended claims.

In accordance with one embodiment, the

present invention contemplates the production of brittle alloys ofnickel and iron by a partial oxidation of the metals constituting themelt. More specifically, the invention contemplates the production ofbrittle nickel iron alloys, generally known as permalloy, in which theproportions of its constitutents are more than 25% nickel and theremainder principally iron, and in one form which has provensatisfactory the nickel content being approximately 7 8 of the whole, bymelting the constituents in an uncovered furnace in the presence ofoxygen and an oxidizing substance, boiling the molten material until itis oxidized, pouring it into a so mold, and rolling the material whilehot into a thin slab to produce a fine crystalline structure.

The preferred method of producmg the Application filed. April 10, 1938.Serial No. 101,179.

brittle, fine grained material in accordance with the invention istoplace the required quantities of nickel and iron in an uncovered(furnace, preferably electrically heated, adding a calculated quantity ofoxidized material of the same urity, andheating until the material is meten, the melting be ing done in an uncovered furnace in order that thematerial may be oxidized by atmospheric oxygen. Since, it virgin metalis used, it requires considerable time to obtain a melt which isoxidized to the right degree, oxidized material is added to furnishadditional oxygen. Iron oxide in the form of iron ore may also be addedto furnish oxygen within the bath. When the material has become moltenit is oxidized by boiling for a length of time determined by the amountof oxidation desired and the type of furnace used. The degree ofoxidation of the material depends upon the length of the melting period,the length of the boiling period, the amount of the surface of the meltexposed to the air, and the amount of oxygen present in the chargedmaterial, and the heating and boiling periods are governed by theVarious charges and the type of furnaceused. Experiments have shown thatthe metal of a melt which is not sufficiently oxidized is not brittle.Consequently to insure the exact amount of oxidation, the melt isheavily oxidized and a small quantity of a. suitable deoxidizer, such asmagnesiumnickel alloy, aluminum or chromium, may be added just beforethe melt is poured. After the molten material has been boiled therequired length of time, it is then poured into an ingot mold, and assoon as the material is solidified, the mold is removed and the ingot isallowed to cool. Samples of the material are taken from various parts ofthe ingot which are analyzed and if the material is of the requiredcomposition it is placed in a furnace where it is heated toapproximately 1325 C. at which temperature it may be easily rolled.

In order to obtain a fine dust, the material should have a very finecrystalline structure which is obtained by successively passing the hotbillets from the heating furnace through progressively reducing rollswhich form the material into a flat strip of about one-fourth of an inchin thickness and five principally along the crystalline boundaries,

the greater the reduction of area of the billet at'ter the last heatingthe finer the grain structure and the finer the dust which can beproduced from the finished product. The rolled slabs are broken intoshort pieces and are then crushed in a jaw crusher, hammer I mill, orany other suitable type of apparatus in which a further reductionoccurs. The

material after .being passed through the jaw crusher is subsequentlyrolled in a ball mill until it is reduced to a fine dust. The dust issieved through a 120 mesh sieve and any residue is reme ted and theforegoing operation is repeated to again reduce the material to afinelydivided form.

By using an alloy of the proport/rdns stated in the preceding paragraphand by following the foregoing method of procedure, a very fine grainedcrystalline product is obtained which is extremely brittle and whichwhen reduced to a fine dust ields a large percentage of particles whichare small enough to pass through what is commonly known as a 200 meshsieve. When reduced to a finel divided form, the material is then in aorm to be used for either continuous, or lump loading of telephonecircuits.

The material is particularly adapted to be formed into rings or coresfor loading coils in the manner more full described in theaforementioned applicat on in which the finely divided particles areheated to a high tern erature, are individually insulated by coating theparticles with an insulator consisting of chromic acid, water glass andtalc, the insulated material formed into rings or cores by theapplication of a high pressure, the rings boiled to render. themchemically stable, and finally annealed to stabilize the insulator andto give the rings the desired magnetic properties. A plurality of ringsthus formed are then stacked coaxially to form a core on which the usualtoroidal winding is applied, the number of such rings used dependingupon the existing electrical characteristics of the telephone circuitwith which the loading coils are to be associated. Since, in order tohave low core losses in loading coll cores made of permalloy dust in theabove described manner, it is centage pass throu h a 200 mesh sieve, itis readily seen that t e material produced according to this inventionis especially adapt- 3. A method of embrittling iron-nickel alloys,which consists in oxidizing the constituents while in a molten state.

4. A method of embrittling iron-nickel alloys, which consists inoxidizing the in redients by means of oxidized metal whic is heated atits melting temperature.

5. A method of embrittling iron-nickel I alloys, which consists inmelting iron and nickel in the presence of oxidized iron-nickel alloyand oxygen.

6. A method of embrittling iron-nickel alloys, which consists in meltingthe ingredi-' cuts in the presence of ox gen.

7. The method of ma ing brittle magnetic alloys, which consists inmelting nickel and iron in the presence of oxygen and boiling the moltenmaterial.

8. The method of making brittle magnetic alloys, which consists inmelting nickel and iron in the presence of oxy en, boilin the moltenmaterial, allowing 1; e materia to solidify, and rolling the materialwhile hot into a strip.

9. The method of making brittle. magnetic allo s composed of more than25% nickel and the remainder principally iron, which consists in meltingthe ingredients in the presence of oxy en and boiling the ingredientsuntil oxidlzed.

10. The method of preparing magnetic materials composed of more than 25%nickel and the remainder principally iron in a finely divided form,which consists in melting the ingredients in the presence of oxygen,boiling the ingredients until oxidized, allowing the material tosolidify, and working the material to produce finely divided particles.

11. The method of preparing magnetic materials in a finely divided form,which consists in melting approximately 78 parts of nickel and 21 partsof iron in the presence of oxygen, boiling the molten material'until'oxidized, allowing the material to solidify, working the material toproduce a change in the crystalline structure and subsequently reducingthe material to finely 1 divided particles.

12. The method of preparing magnetic materials in a finely divided form,which consists in melting approximately 7 8 parts of nickel and 21%parts of iron with oxidized magnetic material of the same purity,boiling the molten material, and work-.

ing the material to produce finely divided particles.

13. The method of preparing magnetic materials in a finely divided form,which consists in melting approximately 78% parts of nickel and 21 partsof iron with oxidized magnetic material of the same urity, boiling themolten material, allowing the material to solidify, working the materialto produce a change in the crystalline structure, and subsequentlyreducing the material to finely divided particles.

14. A method of embrittling magnetic alloys of iron and nickel, whichconsists in heating the ingredients in the open air for a periodsuflicient to cause 'their liquidation and oxidation.

15. A method of embrittling ferrous alloys, which consists in partiallyoxidizing the alloy by heating the ingredients there- 7 of at theirmelting temperature in the presence of an oxidizing agent. I

16. A method of embrittling iron and nickel alloys in which the nickelcontent exceeds 25%, which consists in heating the ingredients in thepresence of free oxygen, allowing the alloy to solidify, and reducingthe alloy to a finely divided .t'orm.

In witness whereof, we hereunto subscribe our names this 3rd day ofApril, A. D., 1926.

CHARLES Plum BEA'I'H. HERBERT MARTIN EDWARD HElNlCKl-I.

